1. Field of the Invention
The present invention relates to a server in charge of a control plane in a mobile communication network and a method of controlling services in the server.
2. Related Art
To respond to new technologies and various forums relating to 4G mobile communication, 3GPP, which defines technology standards for 3G mobile communication systems, started research on long term evolution (LTE)/system architecture evolution (SAE) technologies from later 2004 as a part of its effort to optimize and enhance performance of 3GPP technologies.
SAE, which is primarily led by 3GPP SA WG2, is a network technology directed toward supporting mobility between heterogeneous networks and determining the network structure together with the LTE task of 3GPP TSG RAN. Recently, SAE is one of critical issues regarding 3GPP standardization. For 3GPP systems to be able to support various radio access technologies based on IP, this task has been targeting optimized packet-based systems which can minimize transmission delay with enhanced data transmission capacity.
The SAE upper level reference model defined by 3GPP SA WG2 includes non-roaming cases and various scenarios of roaming cases, and their details are disclosed in 3GPP standard document TS 23.400a and TS 23.400b. One brief network structure is shown in FIG. 1
FIG. 1 is a view illustrating an evolved mobile communication network.
One critical feature of the network structure shown in FIG. 1 is that the network is based on a 2-tier model consisting of eNodeB of evolved UTRAN and gateway of core network. The eNodeB 20 includes, but not exactly comply with, the functions of a NodeB and RNC of the existing UMTS system, and the gateway may have the functions of SGSN/GGSN of the existing system.
Another critical feature is that a control plane and a user plane between an access network and a core network are exchanged with different interfaces. In the existing UMTS system, one interface is present between an RNC and an SGSN, whereas the mobility management entity (MME) 51 in charge of processing a control signal is separated in structure from the gateway (GW), so that two interfaces, S1-MME and S1-U, are used. The GW includes a serving gateway (hereinafter, ‘S-GW’) 52 and a packet network gateway (hereinafter, ‘PDN-GW’ or ‘P-GW’) 53.
FIG. 2 is a view illustrating a relationship between an (e)NodeB and a Home (e)NodeB.
In the 3G or 4G mobile communication systems, an effort to increase cell capacity goes on in order to support bilateral services and high-capacity services, such as multimedia content processing and streaming
The growth of communication and multimedia technologies demands various high-capacity transmission technologies. To increase wireless capacity, more frequency resources may be assigned to users, but assignable frequency resources are limited.
To increase cell capacity, there is an approach of using higher frequency bandwidth and reducing cell coverage. When a cell with small cell coverage—such as pico cell—applies, a higher frequency band than that used in the existing cellular system may be used so that more information may be transmitted. However, more base station needs to be installed in the same area, thus resulting in costs increasing.
As a recent approach to increasing cell capacity using small cells, femto base stations, such as Home (e)NodeB 30, have been suggested.
Starting with RAN WG3 of 3GPP Home (e)NodeB, Home (e)Node 30 is recently being intensively researched by SA WG.
The (e)NodeB 20 shown in FIG. 2 corresponds to a macro base station, and the Home (e)NodeB 30 may be a femto base station. As used herein, the 3GPP terms are basically used, and the term “(e)NodeB” refers to NodeB or eNodeB. Further, the term “Home (e)NodeB” refers to Home NodeB or Home eNodeB.
The interface denoted in dotted lines is provided for control signal transmission between the (e)NodeB 20 and the Home (e)NodeB 30 and the MME 510. The interface denoted in solid lines is provided for data transmission of a user plane.
FIG. 3 illustrates problems with the conventional art.
As shown in FIG. 3, in case traffic at the interface between the (e)NodeB 20 and the S-GW 52 is under overload or congestion or in case traffic at the interface between the Home (e)NodeB 30 and the S-GW 52 is under overload or congestion, downlink data to the UE 10 or upload data from the UE 10 is not correctly transmitted.
Or, even in case the interface between the S-GW 52 and the PDN-GW 53 or interface between the PDN-GW 53 and an internet protocol (IP) service network of a mobile communication service provider is overloaded or congested, the downlink data to the UE 10 or upload data from the UE 10 may not be correctly transmitted.
Further, when UE is handed over from a current cell where the UE is serviced to another cell, if the other cell is in the overloaded state, the service to the UE may drop.
To address such problems, the mobile communication service providers upgrade the S-GW 52 and the PDN-GW 53 to high-performance ones or install new equipment. However, this may result in high costs. As times go by, the amount of data transmitted/received exponentially increases, thus causing overload.
Meanwhile, there are suggested various schemes to optimize the S-GW 52 and the PDN-GW 53 without further establishing mobile communication networks. For example, SIPTO has been suggested—a technology of transmitting specific IP traffic (e.g., internet services) of the UE through a selected optimal path in a macro access network and detouring, in a femto access network (e.g., Home (e)NB), it to a public network, not the mobile communication network—that is, along a path through nodes of a wired network—without transmitting or receiving it through the mobile communication network.
FIG. 4 illustrates the concept of selected IP traffic offload (SIPTO).
Referring to FIG. 4, there is shown a mobile communication system, such as evolved packet system (EPS). The EPS system includes an (e)NodeB 20, an MME 51, an S-GW 52, and a P-GW 53. Further, an Home (e)NodeB 30 is shown.
At this time, as shown, the SIPTO technology detours specific IP traffic (e.g. internet services) of the UE 10 to nodes of a wired network 70 without going through nodes in an IP service network 60 of a mobile communication service provider.
For example, if the UE 10 is allowed to access the (e)NodeB 20, the UE 10 generates a session for passing through the wired network 70, such as a public communication network, through the (e)NodeB 20 and may perform an IP network service through the session. At this time, a service provider's policy and enrollment information may be considered.
In order to be able to generate the session, a gateway—that is, a local gateway in charge of some of the functions of the GGSN in case of UMTS or a local gateway in charge of some of the functions of the P-GW in case of EPS—may be used as one being installed adjacent to the (e)NodeB 20.
As such, the local gateway is called local GGSN or local P-GW. The functions of the local GGSN or local P-GW are similar to those of GGSN or P-GW.
As described above, the SIPTO technology has suggested a concept of generating a session to detour (offload) UE data to a wired network, such as a public communication network, through the (e)NodeB 20, i.e., a macro base station.
However, the conventional SIPTO technology still leaves some problems when the (e)NodeB 20 is overloaded since the technology allows users' data to pass through the macro base station, i.e., the (e)NodeB 20.